Since it's a movie about an actor best known for playing a superhero, it's not entirely strange for the Birdman movie website to have a section of comics. Unexpected, sure, but it makes a certain kind of sense. The story of the film surrounds an actor whose public persona is tied to a superhero film franchise. Comics could help tie the movie more tightly to that superhero's mythology, and flesh out the world of a film in an interesting and engaging way for fans who are curious to find out more.
But here's the thing: The comics on the Birdman website aren't about Birdman at all. Instead, they're about its star, Michael Keaton, telling strange stories about how he was attacked by Michael Douglas and forced to change his name, how a meeting with Chris Farley involved prophecies of death, and, perhaps strangest of all, a long text piece about Courtney Cox's unfortunate super-powers.